The goal of this process was to model the helium-based modular, nuclear reactor power cycle after the existing MIT Pebble-Bed Nuclear Reactor Power Cycle (Kadak, 2005), and to improve on the design by changing the working fluid to supercritical carbon dioxide (s-CO2). The power output of the process as specified in the problem statement, provided by Adam Brostow, was 120 MW. S-CO2 is a much denser fluid, and should theoretically require smaller equipment sizes, making it the more economically viable option for this process. However, it was found that with a return on investment (ROI) of -2.13% and a net present value (NPV) of -$489 million, this process was not economically feasible, due to the high temperatures, pressures, and flow rates required. This process had an electrical output of 118 MW, while the helium met the design condition of 120 MW. The helium process had a ROI of 11% and a NPV of $241 million. For this reason, helium is recommended as the working fluid for a nuclear reactor power cycle of this magnitude.